Interleukin 2 restores CD3-ζ chain expression but fails to generate tumour-specific lytic activity in tumour-infiltrating lymphocytes derived from human colorectal hepatic metastases

Metastatic colorectal cancer is usually progressive despite infiltration of the tumours by T lymphocytes, suggesting that these tumour-infiltrating lymphocytes (TILs) are functionally deficient. Recently, TILs from other tumours have been shown to express reduced levels of the T-cell receptor signal-transducing CD3-zeta chain. We were interested to determine whether a similar abnormality existed in TILs from human colorectal hepatic metastasis (CHM) and, if so, whether correcting the abnormality in vitro would restore anti-tumour activity and provide support for the development of immunotherapy for colorectal hepatic metastases. Twelve of 19 TILs from colorectal hepatic metastases were successfully expanded in vitro in high-dose recombinant interleukin 2 (rlL-2) and their specific anti-tumour cytolytic activity was determined. CD3-positive (CD3+) TILs were HLA-Dr(high) and CD69(high), suggesting that they had been activated by exposure to antigen but expressed low levels of CD25, CD71 and the nuclear proliferation antigen Ki-67, Furthermore, they showed reduced expression of CDB-zeta compared with autologous peripheral blood T cells (PBTs) and failed to proliferate in the absence of high-dose rlL-2. Expansion of TILs in rlL-2 resulted in restoration of CD3-zeta expression and the ability to lyse K562 and Daudi cells but not autologous tumour cells, The absence of autologous tumour-specific cytolytic T-cell (CTL) activity may be due to the poor immunogenicity of colorectal tumour cells, which we found expressed only low levels of MHC I antigens and CD54 and failed to express MHC II antigens or the co-stimulatory molecules CD80, CD86 or CD106. The inability of rlL-2 to generate tumour-specific CTLs despite restoration of CD3-zeta expression and the presence of an intact lytic mechanism suggests that successful immunotherapy may require the development of strategies to increase the immunogenicity of this tumour.